(1) Field of the Invention
The present invention relates to a novel organosiloxane compound suitable for the modification of silicone rubbers and synthetic resins, a novel organosiloxane compound useful as an intermediate, and a process for preparing them.
(2) Description of the Prior Art
Heretofore, a fluorine-containing group has been introduced into silicone rubbers for the purpose of improving oil resistance and solvent resistance. A typical example of the fluorine-containing group is a 3,3,3-trifluoropropyl group, and the fluorine-containing group is usually introduced into a pendant site (branch site of a polysiloxane chain). Such fluorosilicone rubbers have been used singly and in the form of blends and copolymers of these rubbers and ordinary silicone rubbers.
Furthermore, siloxane resins have been used in synthetic resins with the intention of providing the synthetic resins with interfacial characteristics such as repellency, release properties and stain resistance as will as other characteristics such as heat resistance which siloxane compounds have. In these silicone resins, the straight-chain polysiloxane compounds are mainly used. The polysiloxane compound not having any group which is reactive with a synthetic resin is introduced into the synthetic resin by blending them, and the polysiloxane compound having a group which is reactive with a group present in the synthetic resin is introduced thereinto by a chemical bond. The polysiloxane compound can also be used as a raw material of graft polymers for the modification of the synthetic resin to which much attention is paid of late, and particularly in this case, the so-called one terminal-modified polysiloxane compound has been used in which one terminal alone has a reactive group and another terminal is terminated with a trimethylsiloxy group.
The polysiloxane having the functional group only at the one terminal may be prepared by hydrolyzing an organic dichlorosilane or utilizing an equilibrating reaction between a cyclosiloxane and a terminal terminator which is a usual manufacturing process for the polysiloxane. However, this method has the drawbacks that it is hard to obtain the products having a narrow molecular weight distribution, and that it is difficult to attach the functional group only to the one terminal. In place of this method, another method (Japanese Patent Laid-open Publication Nos. 78236/1984 and 275329/1986) has been employed which comprises anion polymerizing of a cyclosiloxane by the use of a trialkylsilanolate compound of an alkaline metal as an initiator, and then reacting the resulting polymer with a trialkylchlorosilane having the desired functional group so as to attach the functional group to the one terminal thereof.
However, when the fluorine-containing substituent is introduced into the pendant site as in conventional silicone rubbers, the fluorine-containing substituent is uniformly present in molded or coated products, and therefore a great deal of the fluorine-containing substituent is required to obtain the expected effect. In addition, there are also troubles due to poor miscibility and a problem such as the adverse influence of the substituents on other physical properties.
Also, when the siloxane compound not having any reactive group for the synthetic resin is used for the purpose of improving the specific characteristics of the synthetic resin, the improvement depends upon the function of the polysiloxane. Thus, the degree of improvement to the synthetic resin is insufficient in view of the fact that the demand of the specific characteristics is now increased. Moreover, in order to obtain the characteristics sought, a great deal of the polysiloxane compound is required, which leads to the problem that the other physical properties are adversely affected. The one terminal-modified siloxane compound also has similar disadvantages, because the other terminal of the molecular chain which has no reactive group for the synthetic resin is terminated with a trimethylsiloxy group. In addition, specific properties such as oil repellency are scarcely improved by the dimethylsiloxane compound alone in which the other terminal is terminated with the trimethylsiloxy group. Also, in the case of a compound having a fluoroalkyl group in its molecule but not having any reactive group for the synthetic resin in the molecule, the specific characteristics deteriorate noticeably with time, and this kind of compound cannot sufficiently provide the resin with the characteristics sought and cannot conveniently be used in graft polymers.
In a conventional manufacturing process of the one terminal-modified siloxane, a trialkylsilanolate is used as an initiator, and thus an additional step is necessary in which a trialkylsilanol is reacted with an alkali metal compound to produce the trialkylsilanolate. In addition, this alkali metal compound (usually a lithium catalyst), which is expensive, is used in an amount equivalent to the trialkylsilanol, and the smaller the molecular weight of the polysiloxane product is and the greater the production of the polysiloxane is, the greater the required amount of the catalyst is. In consequence, the cost of the prepared siloxane compound is high, and for this reason, uses of the siloxane compound are limited.